This article supports the suspicion that many of my former coworkers and I have about ‘tunnel dust’ — the black dust that permeates all of the underground stations — that it may be hazardous to passengers and employees.
The article is about 3 1/2 years old. I’m not aware of any follow-up.
For balance, this article references a study done in the NYC subway system that indicates that while “…the air-borne metal concentrations observed in stations and trains were more than a hundred times higher than above ground”, “airborne levels of the three metals were 100 to 1,000 times lower than OSHA worker-safety limits.” Of course, that begs the question of how the OSHA limits are determined. Also, the article points out that the NYC system is mostly very shallow and has better ventilation rates than deeper systems, like Metro.
This Columbia News Radio transcript offers a different perspective on the NYC study:
NARRATION: While it may not be time for subway riders to head for the exit, what about the thousands of people who work in the subway, spending a good part of their lives underground? The New York City Transit Authority has called steel dust nuisance dust because it doesn’t violate the rules of the Occupational Safety and Health Administration, better known as OSHA.
But Doctor Frank Goldsmith, the Director of Occupational Health for the Transit Workers Union says that OSHA rules are based upon old data that isn’t updated by federal medical standards. He points to steel dust as a perfect example.
TAPE: (GOLDSMITH) It’s composed of manganese and chromium. Chromium is a carcinogen and manganese is a neuropathy problem … which can give you parkinson type outcomes.
In the discussion section, I mentioned that, “While I was working at Metro I contacted OSHA, the EPA, and my congressman among others outside of WMATA. My congressman (Roscoe Bartlett) actually exchanged a couple letters with the chairman of the WMATA Board over a safety issue I raised with him — the black metalic ‘tunnel dust’ that permeates all of the underground stations. The chairman “misinformed” him about what was being done and of course nothing ever changed. Passengers and employees are still sucking tunnel dust into their lungs every day. In fact, the problem is getting worse.”
“RCB & Associates Management” then asked:
“Would you hazard a guess in your opinion that this is brake dust from the trains?”
My reply follows:
“I haven’t seen any test results, but yes, I would say it’s a safe bet that a good portion of the ‘tunnel dust’ is from brake pads and rotors.
[I was in Automatic Train Control (ATC), not Car Maintenance (CMNT), so my knowledge of how rail cars work is limited, but I believe the following is fairly accurate]:
For those who aren’t aware, the braking system on a rail car functions similarly to those on hybrid vehicles. They have both “dynamic” and traditional friction braking. The dynamic brakes function by turning the traction motors (the motors that move the train) into generators and connecting them to a load. On the older rail cars, the load was a bank of resistors mounted under the train. In this way, the kinetic energy of the train was turned into heat (which would simply dissipate and be wasted). The resistors could get extremely hot and in some cases would ignite fires. The newer rail cars actually feed energy back into third rail, using that as the load. Below a certain speed (say 10 to 12 mph?) the friction brakes are used to bring the train to a stop.
The friction brakes are essentially very large, heavy-duty, vented disc brakes. The brake pads are fairly ‘aggressive’ and eat into the surface of the rotors. So the portion of the tunnel dust that comes from the brakes is composed of both pad material and iron.
When I worked at Grosvenor (A11), I had one of those magnetic business cards on my locker. The surface was originally white. After just a few weeks it had turned black — this was on a vertical surface, inside the train control room (TCR). It became clear over the years that many people in Metro management did not care about the front line employees or our working conditions, but you’d think they might care about the ATC equipment. While I can’t prove that the tunnel dust has been the primary cause of any failures, having metallic dust everywhere obviously isn’t a good environment for electrical and electronic equipment.
At one point, back in the late ’90s, I brought a Honeywell HEPA filter in to work and put it in the A11 TCR. It was large and relatively expensive. I set it on top of the equipment cabinet directly in front of the HVAC air return vent. It was destroyed within 2 months. The filter had loaded up with tunnel dust and the motor was straining so hard to pull air through that the bearings failed. I still have the unit and the filter. Keep in mind, it was located at the air _return_, the supply would have been even dirtier.
Metro claims that years ago OSHA or the EPA tested the air in a station and determined that it was safe. I’ve never seen that data (if it even exists). In fact, when I was trying to get something done about the dust, I called the local and federal offices of both the EPA and OSHA and was blown off by all of them. One office, I believe it was OSHA, actually sent me a letter that said OSHA has no jurisdiction on WMATA property. In other words, once again the 51st State (aka the Evil Empire) does whatever it wants.
Maybe the tunnel dust isn’t a problem for either humans or equipment, but without any objective data I find that hard to believe.
Installing high quality air filters would significantly reduce the problem. Some air handlers have no filtration at all — the filters were neglected for so long that they disintegrated and were never replaced. When there are filters installed, they are those ineffective ones that use glass fiber that is so porous you can see your hand through it. They won’t trap anything much smaller than a tumble weed. At one point I spoke with a gentleman who had sold electrostatic filters to the NYC subway system (MTA) because the MTA was concerned about tunnel dust in their system. Electrostatic filters are the type that use an electrical charge to trap particles, as opposed to mechanical filtration like HEPA filters. They are more expensive up front but save money in the long run. Anyway, I gave him a couple contact numbers at WMATA and he got in touch with the appropriate people and offered to install a filter completely free of charge as a demo. They declined. He tried a few more times but finally gave up.
For anyone who doesn’t know what tunnel dust is, it can be found on just about any horizontal surface in any underground station that isn’t cleaned regularly.”
Tunnel dust may not be hazardous, but if it is I would be willing to bet that Metro and our local and federal governments would attempt to downplay the risk because if passengers became sufficiently concerned many of them might stop riding and choose to drive instead, adding to our huge traffic and air pollution problems.
It seems like the jury is still out on this one.